Although the invention will be described with respect to railway wagons, the invention is to be understood to have application to other general forms of bulk carrier, for example road vehicles. The invention has application to the transport of bulk materials such as wheat, coal, iron ore, granular materials in general, or other solid particulate matter.
In prior art vehicles, the bulk material is stored in hoppers which have discharge openings at the base closed by doors. The doors are operated by levers which are driven "over-centre" to maintain the door shut. The over-centre levers are actuated either manually or by hydraulic or pneumatic cylinders rotating a shaft to which the over-centre levers are attached. A further manually operated lever arm is often provided should an actuating cylinder fail. Each hopper is normally provided with a pair of doors opened in unison. In order to operate the hopper doors, considerable physical exertion or a source of hydraulic or pneumatic power is required. The latter situation complicates the mechanical features of the vehicle and hence the reliability of operation as well as the cost of manufacture of the vehicle.
The discharge of particulate materials produces a dust laden atmosphere which can reduce the reliability of hydraulic or pneumatic actuators.
In other prior art, rollers on the end of door levers in cooperation with cams at trackside have been described, such as in Australian patent application No. 53,389/69 (Dorey) or in Miller, U.S. Pat. No. 3,633,772, the cams being moved into the path of the associated door operating mechanism as required. Both of these discloses involve complex mechanisms to operate doors, which mechanisms in turn become inundated with dust when operated since longitudinal door openings are used and have no provisions for preventing accidental collision therewith, for example with the locomotive pulling the wagons.